1991091110101 has 4 divisors (see below), whose sum is σ = 1992256173900. Its totient is φ = 1989926046304.

The previous prime is 1991091110081. The next prime is 1991091110207. The reversal of 1991091110101 is 1010111901991.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1426149466225 + 564941643876 = 1194215^2 + 751626^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1991091110101 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991091150101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 582529336 + ... + 582532753.

It is an arithmetic number, because the mean of its divisors is an integer number (498064043475).

Almost surely, 2^{1991091110101} is an apocalyptic number.

It is an amenable number.

1991091110101 is a deficient number, since it is larger than the sum of its proper divisors (1165063799).

1991091110101 is a wasteful number, since it uses less digits than its factorization.

1991091110101 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1165063798.

The product of its (nonzero) digits is 729, while the sum is 34.

The spelling of 1991091110101 in words is "one trillion, nine hundred ninety-one billion, ninety-one million, one hundred ten thousand, one hundred one".